A conversation I had last summer with a major player in the state DFL Party has stayed with me as the city election campaigns have unfolded in Minneapolis and St. Paul.

“Are you worried that we’re witnessing the start of a split in your party?” I asked, expecting a dismissive reply.

“Off the record?” he said. I nodded assent to shielding his name. “Yeah, I am,” he answered.

His candor has colored my thinking as I’ve watched Our Revolution evolve from the ragtag remnant of the 2016 Bernie Sanders presidential campaign into an organized force in two cities that until lately were considered one-party towns. Our Revolution verges on being potent enough in some urban quarters not just to supplement the DFL Party, but to supplant it.

Or divide it.

That possibility dawned in recent weeks as some Minneapolis leaders of long standing coalesced into an organized counterforce to Our Revolution, particularly in the contests for the city’s Park and Recreation Board. If that counterforce sticks together after Tuesday’s election, takes a name, raises money and recruits candidates for the next cycle — and Our Revolution does the same — what then?

Our Revolution has been described as the liberal version of the circa-2010 Tea Party on the right. The Tea Party pushed the GOP establishment in a more libertarian direction, they noted, but didn’t split the party.

That’s well-noted. And that was before Trump.

Since the disrupter-in-chief arrived in the White House, the American propensity for conflicts of both the intraparty and interparty kind has increased. So says a new “political typology” study by the esteemed Pew Research Center. It does a deep dive into the national psyche every third year to plumb for attitudes and values about government.

Pew reported finding “deep fissures” among adherents to both of the two big parties. Unsurprisingly, it found that Democrats and Republicans are more polarized from each other than at any point in the past 30 years. More surprising was this: “The divisions within the Republican and Democratic coalitions may be as important a factor in American politics as the divisions between them.”

Pew does not go so far as to predict party crackups. But it shows anyone hellbent on division where the cracks are.

Trump has the approval of the vast majority of committed Republicans, Pew found. But they fracture on questions of immigration, trade, the nation’s role in the world and the fairness of the American economic system — suggesting that trouble lies ahead within the GOP house as Trump presses his agenda on those matters. Another, similarly sized cohort of less-committed Republicans — only about two-thirds of whom approve of Trump’s performance — are themselves divided into trusters and mistrusters of big business.

Those findings should fire the imaginations of Republicans who fancy an intraparty challenge to Trump in 2020.

More pertinent to this year’s developments in Minneapolis are Pew’s findings about Democrats. While “largely united in staunch opposition to Trump,” the Democratic coalition is dividing along lines of race and class, Pew reports. White, affluent Democrats are pro-government. The less-affluent, who are also more likely to be people of color — the “disaffected,” in Pew’s nomenclature — aren’t satisfied with government or their opportunity to have a say in running it.

Let those differences play out in a place where easy access to the ballot is the rule and politics is a favorite local pastime — Minneapolis, for example — and factions can morph into rival slates of candidates. Turn loose the unsubtle rhetoric of social media, and something like what news reports last week were calling “a civil war in the Minneapolis DFL” can erupt.

So much for the hopeful notion that a switch to ranked-choice voting would tamp down negative campaigning. Candidates themselves may not be leveling their meanest rhetorical guns directly at one another. But independent political-action committees have exhibited no restraint.

Witness the smear job perpetrated against St. Paul mayoral candidate Melvin Carter by Building a Better St. Paul, a PAC funded by the St. Paul Police Federation, the St. Paul Area Chamber of Commerce and Teamsters Local 120. It scurrilously attempted to link a theft of Carter’s father’s police pistols in August to the rise in shootings in the capital city this year.

Minnesotans will see in a few days how that kind of sharp-elbows campaigning worked in the ranked-choice elections in Minneapolis and St. Paul. But I suspect that residents of the state already sense this: Harshly negative campaigning is part of the reason America’s two big political parties are themselves at risk now.

America’s political professionals have become masters at revving up animosity toward the opposite party. For several decades, they’ve practiced what deserves to be called “base politics,” in both senses of that term. They’ve sought to intensify the motivation to vote among their own supporters — their bases — by demonizing their opponents. Their tactics are a turnoff, depressing voter turnout and the citizenry’s confidence in government. But those are long-term considerations in an enterprise that handsomely rewards short-term gain. A minority that can generate angry loyalty can win.

As a result, majority rule has suffered. Even advocacy groups in whose interest it is to amass majority support for their cause — the St. Paul Police Federation comes to mind — act as if they no longer know how that’s done.

It was only a matter of time before practitioners of base politics turned their toxic tactics on their rivals within their own parties. That’s what has happened this year in Minneapolis and St. Paul. And no matter the outcome of Tuesday’s election, it’s going to take a lot of intraparty healing for these two cities to be seen again as one-party towns.

Lori Sturdevant is a Star Tribune editorial writer and columnist. She is at lsturdevant@startribune.com.

Lori Sturdevant is a Star Tribune editorial writer and columnist who has written about Minnesota government and politics since 1978. She is also the author or editor of 11 books about notable Minnesotans.